Rechargeable lithium batteries are the electrical energy storage devices of choice for many energy storage applications because they have the highest energy density of all known batteries. The most common rechargeable lithium batteries are composed of lithium intercalating transition metal oxides, exemplified by lithium cobalt dioxide (LiCoO2), as cathodes, and either lithium intercalating carbon and metal oxides such as lithium titanium oxide (Li4Ti5O12) or metallic lithium (Li) as anodes.
There are different types of rechargeable lithium batteries classified according to the type of electrolytes they contain. The most common rechargeable lithium batteries, known as lithium ion (Li-ion) batteries, as used to power laptop computers, cell phones and digital cameras, contain organic liquid electrolytes. Other types of rechargeable batteries are based on organic polymer or gel polymer electrolytes and utilize the same kinds of anodes and cathodes as those in the liquid electrolytes. Further types of rechargeable batteries are based on inorganic solid-state electrolytes, again with lithium intercalating transition metal oxides as cathodes and either lithium intercalating transition metal oxides or lithium metal as anodes.
A major drawback of rechargeable lithium batteries containing organic electrolytes whether they are liquid, gel polymer or solid polymer electrolytes is flammability hazard and as a result a solid-state rechargeable lithium battery utilizing all inorganic materials as electrolyte and electrodes has been a desirable concept for many years.
Conventional inorganic solid-state lithium batteries are thin film devices as described in a review by Nancy Dudney in Materials Science and Engineering, volume B116, pages 245-249 (2005). In order to fabricate these batteries, the cathode and anode electrodes and the solid-state electrolytes are deposited layer by layer by magnetron sputtering or other vacuum deposition technique. The anode, the solid electrolyte and the cathode layers are usually a few microns thick each. Also the anode and cathode layers do not contain any electrolyte in them and ion transport through the anode and cathode layers necessary to carry out battery discharge and charge take place in the crystal lattices of the electrode material themselves. As a result, thicker layers of the anode and cathode electrodes cannot be used in these thin film batteries because they will increase the internal resistance of the battery and limit performance including power output and the energy density. These conventional solid-state batteries are considered thin film two-dimensional batteries with low power and energy densities limiting their applications to low power consuming devices such as radio-frequency transmitters, backup power for CMOS memory devices, EKG and other medical sensors, and MEMS devices. Many U.S. patents including, U.S. Pat. Nos. 4,826,743; 5,314,765; 5,338,625; 5,512,147; 5,561,004; 5,567,210; 5,569,520; 5,597,660; 5,612,152; 5,705,293; and 6,398,824, describe various modifications of two-dimensional solid-state thin film lithium batteries. All of the solid-state batteries or improvements described in these patents have the general features of thin film electrode and electrolytes deposited layer by layer by a high vacuum deposition technique.